A summation sign, also known as a sigma symbol, represents the sum of a series of numbers. However, there are other synonyms for this mathematical symbol. One term is the "sigma notation" which is derived from the symbol itself. Another synonym is the "summation operator" which emphasizes its function to sum up the sequence of numbers. Additionally, it is sometimes called a "summation symbol" or "summation notation". The use of different terms for the summation sign may vary depending on the discipline or field of study, but they all refer to the same mathematical concept of summing up values in a series.